1. Field of the Invention
The invention relates to a method for joining blanks or structural components of steel to those of aluminum alloy or titanium alloy, and it comprises turbochargers obtained by the method.
2. Discussion of Background
The joining of different materials plays a considerable part in the highly developed fabrication technology, since frequently different properties are demanded within one arrangement, which properties cannot be obtained by a single material so that, depending on the manufacture and operating function, different materials are used for individual elements of a component or of a structure, in order to arrive at an optimum of economical manufacture and mechanical property.
Thus, for example, according to European Patent Specification 0,129,311, aluminum or aluminum alloy is used, for reasons of manufacturing technology, for the compressor rotor of a turbocharger and, because of the good mechanical properties such as strength and toughness, tool steel is provided for the shaft to be fitted on or for the fixing component for the latter, and these are to be joined to one another by friction-welding.
Some difficulties arise, however, in following this recommendation since, although aluminum can be joined to steel by friction-welding under certain conditions, making a welded joint between steel and hardenable aluminum alloys causes great difficulties.
Likewise, friction-welded joints, capable of being loaded, between steel and titanium alloys have hitherto not been achieved.